afternoon. dancers range from 7 to 18. >> they've been busy. thanks for watching. tonight on "world news," disaster in the pacific. the last big gamble. the japanese about to flip a switch and try to turn on the damaged pumps at the nuclear site. with backup pumps from america on the way. as new video shows what's happening inside the reactors. who will be the new volunteers to go in and brave the radiation? and throughout japan, more anxiety, less food and water. as the president tells americans there is no sign dangerous radiation is coming here. good evening. as we come on the air tonight, the u.s. navy is now racing to the rescue in japan. where there is word that

electricity is about to return to the fukushima nuclear plant, and the u.s. is flying in five giant pumps from a navy base in nagasaki. they are pumps that can deliver enormous amounts of water, after we all watched today as the helicopters tried to spray water, but to no avail. our reporters are out in force on the story tonight. and we will go to japan in a moment. but first, let's head to martha raddatz who has been talking all day to the u.s. officials who are now helping the japanese. martha? >> reporter: diane, every day, the nuclear monster seems to get more frightening. but there is some hope tonight from that big u.s. push to send in water pumps. this coming after last ditch efforts by the japanese failed. one expert told us it's like using a squirt gun to put out a forest fire. japanese fire trucks using riot control water hoses to tackle red hot nuclear reactors.

helicopters swooping overhead, dropping bucket after bucket. every effort falling short. but here is the encouraging news. japanese plant operators have connected a new electric power line to the plant. this entire crisis began when the power was knocked out. if the japanese flip the switch but those critical water pumps to cool the reactors don't work, then it's american pumps to the rescue. the pentagon has shipped high pressure pumps, but no u.s. personnel. once again, the japanese will have workers willing to risk their lives operating them. today, for the first time, a closeup look at how dire things are. you can see reactor three, charred and billowing steam. but look right there. reactor four. you can see a green structure. now look at this old photo taken inside. the same green structure above the critical fuel rod pool.

now, the walls are blown out. one u.s. official telling us tonight, "this is close to a crisis situation." the water in the pool is desperately low, if there is any left at all. without water, the rods will ignite and fill the sky with radioactive smoke. and at reactor three, the fuel stored in its pool is likely on the verge of melting, including plutonium, which, if it melts down, could produce a highly dangerous toxic plume. also, its critical five-foot thick containment vessel is likely cracked. if the core melts down, it will pool up at the bottom of that vessel and could seep out, core on the floor, a devastating breach that would mean radioactive plumes released. if you wonder why these pumps weren't sent in earlier, it's because the japanese did not ask for them. as one u.s. official told me, i think they are finally beginning to understand just how critical this is.

something they didn't seem to believe for far too long, diane. >> hard to believe they didn't believe for so long. but martha, a question we ask every day about radiation. what can you tell us tonight about exactly how much radiation has escaped around the concentric circles around that plant? >> reporter: well, we've got some really interesting statistics, diane. if you are inside the plant, there's the equivalent of as many as 10,000 x-rays an hour. at the gate, the workers are getting as many as the equivalent of 250 x-rays an hour, or one c.a.t. scan. just outside that japanese evacuation area, that's about 12 miles, as high as two x-rays an hour. and just outside the u.s. evacuation zone, and that's about 50 miles, as high as one x-ray every two days. you can see why they evacuated from those areas, diane. >> martha, thank you. and now, we want to learn more about the 140,000 japanese people that are living in that ring, between those 12 and 19

miles from the plant. they've been told to stay inside, to seal the windows of their homes. but is that enough to keep them safe? clarissa ward has been traveling through the heart of this disaster and reports from japan tonight. >> reporter: this nursing home just 15 miles from the stricken plant. buses won't come close enough to evacuate the patients, but the doctors and nurses won't leave without them. "my family has already evacuated and i want to run to join them. but i'm hanging on and continuing my work here." cut off from the outside world, conditions are beginning to deteriorate. "i have no oil left," this man said. "and no means to take care of myself." the japanese government has ordered everyone within 12 miles of the fukushima plant to evacuate. and told people up to 19 miles away to close their windows and stay inside. the u.s. is more cautious, ordering americans within 50 miles to leave. so, does closing your doors and windows and staying inside really protect you from a nuclear accident?

experts say yes. >> number one, it prevents you from breathing in particulate radiation. it also protects you from being contaminated. and thirdly, it could offer some shielding from radiation that is on the outside. >> reporter: in the japanese capital, no one is panicking yet. but some are choosing to leave the city as a precautionary measure. here in osaka, even further to the south, we find a family of four at the train station, arriving from tokyo. do you think that the japanese government is being straightforward about what's going on? >> translator: no, i don't think so. >> reporter: the bigger the ring you draw around the plant, the harder it is to evacuate. so, there are 70,000 people in the current evacuation zone of 12 miles. but going out to 50 miles, which is u.s. considers safe, you're talking about potentially evacuating 1.9 million people. diane? >> clarissa reporting from japan tonight. clarissa ward.

and as martha said to us, another band of brothers in japan is being asked to make the ultimate sacrifice. more japanese workers being asked to go inside that plant and an almost certain death sentence. it is that last ditch effort to save their countrymen and david muir, just back from the quake zone, looks more closely tonight at the physical details of the danger they choose to face. >> reporter: we have not seen their faces yet, but the world knows their valor. and today, what appears to be the first words from one of the workers at fukushima. "in the middle of the tsunami alert last friday, at 3:00 a.m. in the night, when we couldn't even see where we were going, we carried on working to restore the reactors with the realization that this could be certain death. as the hours turned to days, fighting fatigue and empty stomachs, we dragged ourselves back to work. there are many who haven't gotten in touch with their family members." and they know what history has shown us all. that radiation is an impossible enemy. the russian submarine, k-19, that catastrophic radioactive leak in 1961.

eight crew members determined to supply coolant. some dying within just six days. and of course, chernobyl. an engineer at reactor four remembers. he stumbled upon a coworker. >> he was covered in this mix of water and steam, radioactive steam. i struggled to put him onto my back. i got burns here, on my back, on my buttocks. you can see, because it was damp, and the stuff went through my clothes. see? and it burned me. >> reporter: this, as other workers were sent in to cool the rods, much like they're trying to do today in japan. and in just the first hour -- >> they were suffering from nuclear tan. their skin went black. their skin was floating and blisters were appearing on their skin within a couple of hours. they began to vomit. some of them died within two or three days. >> reporter: a chernobyl shift commander would later tell "the new york times," "you had the impression you could see the

radiation. first, a lot of the substances there were flowing, luminescent, a bit like sparklers." and the gas on the roof? "this was a kind of fog. it gave off a peculiar smell." and like those faces of chernobyl, the waves as people were bussed away. tonight, those workers in japan are fighting to save their own towns, their own families. >> and you were in fukushima, david, and welcome back home. but do you have a sense of the word of what it is that drives these workers to elect this? >> reporter: everyone i spoke to today said it was like the faces you saw from the vintage video from chernobyl. i met all those families along the evacuation zone, diane, and those people tell me that those workers inside the plant are fighting not only to save the plant but to save their family, their towns and all those people that they are certain are evacuating. >> so, they keep the faces in their minds when they volunteer. david muir back here at home tonight. and also here at home, of course, there has been concern about how much radiation might come here.

all eyes on the plumes of radiation hurtling across the pacific. this is just a model of what might happen, toward our shores. the first of the plume expected to hit california tomorrow. but today, president obama went out of his way to stress there is no need for alarm here at home. >> so i want to be very clear. we do not expect harmful levels of radiation to reach the united states, whether it's the west coast, hawaii, alaska or u.s. territories in the pacific. let me repeat that. we do not expect harmful levels of radiation to reach the west coast, hawaii, alaska or u.s. territories in the pacific. >> the president asking americans to stand down from their alarm. and at the same time, the u.s. is deploying radiation detectors up and down the west coast to make sure this is the case. neal karlinsky in seattle tells us about them.

>> reporter: it may not look like much, but if radiation from japan makes its way into the air over the western u.s., this sensor south of seattle will be among the first to know it. >> this disc right here that you can see is the filter that is monitoring, that is pulling air through it. >> reporter: the federal government has 100 of these sensors running around the clock, covering about 70% of the country's population. they send data directly to computers at the epa, and so far, they have detected no increase in radiation. >> there's a lot of space between here and japan, so, we don't expect an impact here, but we want to make sure. >> reporter: and in the face of concern about fallout making it across the pacific, extra radiation sniffers are being sent to points of likely first contact, in guam, hawaii and alaska. detection, they say, is the easy part. now, they just have to convince a jittery public to breathe easy. the air is safe. neal karlinsky, abc news, seattle.

now, i want to bring in our chief health and medical editor dr. richard besser for a kind of reality check. the president reassuring today about the possibility of dangerous radiation here. are you reassured? >> reporter: i am reassured. you know, when i listened to the president, when i talked to people all day throughout government in terms of what's being done to prepare, what they've learned from chernobyl and other events, i'm reassured we're not going to see harmful levels of radiation in this country. that doesn't mean they won't measure any, but harmful levels is very different. >> and you were saying to me, don't take the pill, don't take that potassium iodide pill. >> reporter: no, you don't want to do that. there's side effects. there's dangers to taking that pill. if you have that pill, put it away, know where it is. but don't take that pill. >> and we remember after chernobyl, the particular concern was milk, milk for children. is that a particular concern here, even if there isn't general population danger. >> reporter: this is, i think, a secondary tragedy from chernobyl. the children who developed thyroid cancer didn't do it necessarily from the initial release.

what happened was, radioactive iodine fell on the grass and was eaten by cows. and that went into their milk. children drank that milk over a long period of time and that led to almost 4,000 cases of cancer in that area around chernobyl. here in the united states, they are preparing to be able to monitor the food supply, the milk supply. if it's necessary. so, that kind of a disaster is not something we need to worry about. >> dr. besser adding to the reassurance tonight. and, as the nuclear crisis flirts with disaster, a reminder that the human crisis already has hit epic proportions. 1.6 million homes are without water. and they are the lucky ones, because nearly half a million japanese are homeless. tonight, a brigade of good samaritans springing into action to help a nation still reeling from the moment of impact. new pictures tonight of what it was like to try to outrun the monster tsunami as it began to descend.

these people find shelter. others did not. a woman climbing to safety with the help of a fire hose. "thank you," she tells her rescuers. "thank you. i thought i was going to die." some of the rescuers helping others through their own grief. this volunteer firefighter, for the first time, sees his own family is gone. "my wife, my son's family and grandchildren," he says. "i lost them all. i can't take it." in a neighboring town, water and mud flood a hospital. ruining the medical equipment. but with the help of the dedicated staff, every patient survived. and in sendai, at this home for the elderly, the care givers made an extraordinary decision not to evacuate.

they knew the shelters would not be able to care for their patients. so, they somehow managed to gather them up and get them up to a top floor and bunker down. the tsunami wiped away everything around them, but not the people inside. all of these survived, too. and when the tsunami hit, this woman and her mother first swam on top of their own home's cupboard and lived for three days there in the freezing cold. and now, they are alive because of a daughter's love. she carried her 88-year-old mother on her back to safety. to warmth. to hope. carried her on her back. and still ahead on "world news," they are shutting down some nuclear reactors in europe. should america be shutting some down here at home?

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yesterday, germany decided to shut down seven of their oldest nuclear reactors for inspection. so, everyone was wondering what president obama would say about the 104 reactors here in the united states. we have the answer now from dan harris. >> reporter: the timing could not be trickier for the president. just as the country is about to make a big new investment in nuclear power, japan happens, which has resulted in widespread fear among the general public and on capitol hill. >> we go in and we decide what the earthquake risk is, and mother nature says, excuse me, you didn't ask my opinion. and that's a fact. >> reporter: today, mr. obama did call for a safety review, but he also said nuclear power is still an important part of our energy future. >> our nuclear power plants have undergone exhaustive study and have been declared safe for any number of extreme contingencies.

>> reporter: but that may not silence the critics, some who point to what germany is doing. shutting down its oldest nuclear power plants for three months for safety checks. late today, congressman ed markey told us america should look at doing the same thing. >> the life expectancy of these plants has been extended from 20 years to 40 years to longer. as a result, they each need to be taken in for a checkup. >> reporter: here in the u.s., about half of our reactors are more than 30 years old. also, 11 of them sit in active earthquake zones and 16 plants use the same kind of reactors that are in so much trouble over in japan right now. so, we put the question directly to a spokesman for the american nuclear industry. can he look americans in the eye and say our plants are safe in the event of a catastrophe? >> i can absolutely look every american in the eye and make the solid statement, u.s. nuclear power plants are safe. >> reporter: abc news contacted more than a dozen nuclear

experts, all over the country today, and overwhelmingly, they agreed that american nuclear power plants are safe. so, why do they say that? well, first, because they say america has the toughest regulations in the world. second, they say, after 9/11, our plants made extensive safety improvements, specifically to handle the sort of problems they're dealing with in japan right now. but diane, they admit, they cannot plan for everything. no guarantees. >> but no need to shut down to inspect? >> reporter: not thus far, they say. >> all right, dan harris, thank you. and when we come back, other news, big news, from libya tonight. oporosis slow me down? so i asked my doctor about reclast because i heard it's the only once-a-year iv osteoporosis treatment. he told me all about it and i said that's the one for nana. he said reclast can help restrengthen my bones to help make them resistant to fracture for twelve months. and reclast is approved to help protect from fracture

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and get the all day pain relief of aleve in liquid gels. and we have big news now about the conflict in libya. the u.s., france and britain are said to be readying possible military action after the united nations security council voted late today to authorize air strikes. moammar gadhafi went on television and made a vow to crush the rebels in his own country, saying he would show them no mercy. and so, the u.n. acted. and one upbeat note tonight about how long we're living in america. new findings show life expectancy in this country has hit an all-time high. an estimated 78 years, 2 months, for a baby born in 2009. researchers say progress keeps being made in medical treatment, vaccinations and the fight against smoking. and, coming up, how some

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[ male announcer ] you should not take reclast if you're on zometa, have low blood calcium, or kidney problems. or if you're pregnant, plan to become pregnant or are nursing. take calcium and vitamin d daily. tell your doctor if you develop severe muscle, bone or joint pain, if you have dental problems, or if you develop new or unusual pain in your hip, groin, or thigh. the most common side effects include flu like symptoms, fever, muscle or joint pain headache, nausea, vomiting and diarrhea. share the world with the ones you love! and ask your doctor about reclast. once-a-year reclast. year-long protection for on-the-go women. and finally tonight, it's been said that sometimes a caring heart is more healing than any medicine. and tonight, some small

citizens, some of them japanese-american. children, trying to comfort children halfway around the world. >> it's an island off of china. >> across the ocean. >> reporter: 5 years old, looking out at a world far away. but wanting to help. >> can someone tell me what happened in japan? >> a earthquake. >> tsunami. >> people died. >> i wish this didn't happen. >> reporter: one shy little boy tells us in japanese there was lots of water. and houses floated away. with crayons and markers they show us how they think it must have been as people and houses were surrounded by so much destruction. and then they sat down to write. >> i'm writing to my mom's best friend because i hope he's okay because he's my best friend, too. >> i hope you get your toys back.

>> i hope you're okay. >> reporter: one class of school children in america sending simple messages of comfort. >> please don't cry. >> reporter: to children like them, 5,000 miles away. hearts, rainbows, family and -- >> i love you. >> oh for a rainbow for the japanese children. thank you for watching tonight, we're always on abcnews.com. and we'll see you tomorrow. tonight the japanese nuclear crisis and why even a worst-case scenario is little cause for concern. >> tonight why pg&e wants to down grade the earthquake threat of this california nuclear power plant. >> angry voice mail messages

from barry bonds, thrown out of court. his perjury trial draws near. >> and the state's budget impass deepening over the threat of being called a traitor. >> good evening. the japanese power company announced it's hours away from restoring electricity to two of the six reactors at the nuclear plant. >> getting power could help cool down the other reactors. a second round of water drops could soon begin, as well. they've been using helicopters to dump bucket loads of water and used water cannons from the ground. tokyo electric says radiation levels are down slightly. the state department warned americans to consider leaving japan and offered to evacuate families of the u.s. government personnel. death toll stanldz at 5600